Python file operation method (file reading and writing, random reading and writing, file encoding)

def main():
    try:
        # 这里加不加r其实都一样,默认的就是r xxxx自己替换成你的文件名字
        file = open("E:\\xxxx", "r");
        print("文件名称：{}".format(file.name));
        print("文件是否已关闭：{}".format(file.closed));
        print("文件访问模式：{}".format(file.mode));
    except BaseException:
        pass;
    finally:
        file.close();
        print("调用close()关闭文件对象");

if __name__ == '__main__':
    main();

def main():
    try:
        # w代表输出 文件不存在时，自动创建，创建成功之后写入数据
        file = open("E:\\test.txt", "w");
        file.write("奥特曼打小怪兽");
    except BaseException:
        pass;
    finally:
        file.close();

if __name__ == '__main__':
    main();

Use with to perform file operations

def main():
    with open("E:\\test.txt","w") as file:
        file.write("黑猫警长抓小老鼠");

if __name__ == '__main__':
    main();

The a of the test file operation represents appending data to the file

def main():
    with open("E:\\test.txt","a") as file:
        for item in range(10):
            file.write("黑猫警长抓小老鼠\n");

if __name__ == '__main__':
    main();

Use r to read the contents of the file

def main():
    # 使用r来读取数据
    with open("E:\\test.txt","r") as file:
        # 读取一行
        var = file.readline();
        # 当一行数据存在时
        while var:
            print(var,end="");
            # 继续读取下一行
            var = file.readline();

if __name__ == '__main__':
    main();

Use r to read file content optimized version

def main():
    # 使用r来读取数据
    with open("E:\\test.txt","r") as file:
        # 迭代文件对象
        for line in file:
            # 输出每行内容
            print(line);

if __name__ == '__main__':
    main();

Random read and

output the file according to the format

#将文件按照既定格式进行输出
NAMES = ("zhangSan","liSi","wangWu");
AGES = (1,2,3);
def main():
    with open("E:\\test.txt","a") as file:
        for item in range(len(NAMES)):
            content = "{name:<10}{age:>4}\n".format(name = NAMES[item],age = AGES[item]);
            file.write(content);


if __name__ == '__main__':
    main();

Read the data from the specified location of the file

def main():
    with open("E:\\test.txt",mode = "r") as file:
        # 忽略前15位的数据
        file.seek(15);
        print("【第二行数据】，当前位置：{}，姓名：{}，年龄：{}".format(file.tell(),file.read(10).strip(),int(file.read(5))));
        print("【第三行数据】，当前位置：{}，姓名：{}，年龄：{}".format(file.tell(),file.read(10).strip(),int(file.read(5))));


if __name__ == '__main__':
    main();

Use seek to relocate the file

def main():
    with open("E:\\test.txt",mode = "r") as file:
        # 忽略前15位的数据
        file.seek(15);
        print("【第二行数据】，当前位置：{}，姓名：{}，年龄：{}".format(file.tell(),file.read(10).strip(),int(file.read(5))));
        file.seek(0);
        print("【第一行数据】，当前位置：{}，姓名：{}，年龄：{}".format(file.tell(),file.read(10).strip(),int(file.read(5))));
        file.seek(30);
        print("【第三行数据】，当前位置：{}，姓名：{}，年龄：{}".format(file.tell(),file.read(10).strip(),int(file.read(5))));


if __name__ == '__main__':
    main();

Directly locate the data you want to read to avoid invalid performance expenses. The disadvantage is that you need to specify the file format to analyze

# 姓名的内容长度为10
NAME_LENGTH = 10;
# 年龄的内容长度为10
READ_LENGTH = 5;
# 保存数据读取的行数
line_count = 0;

def get_age():
    # 当前的偏移量
    seek_offset = 0;
    with open("E:\\test.txt", mode="r") as file:
        # 持续进行内容的读取;
        while True:
            # 读取年龄的位置
            file.seek(seek_offset + NAME_LENGTH);
            # 读取数据长度
            data = file.read(READ_LENGTH);
            # 可以获取到data数据
            if data:
                # 引用全局变量
                global line_count;
                # 统计的行数追加1
                line_count +=1;
                # 修改读取偏移量
                seek_offset = file.tell();
                # 局部返回
                yield int(data);
            else:
                # 结束函数调用
                return;
def main():
    sum = 0;
    for age in get_age():
        sum +=age;
    print("一共读取了：{}条信息,用户平均年龄为：{}".format(line_count,sum/line_count));

if __name__ == '__main__':
    main();

file encoding

def main():
    message = "奥特曼-打小怪兽".encode("GBK");
    print("编码后的数据类型为：{}".format(type(message)));
    # 输出为二进制数组
    print(message);


if __name__ == '__main__':
    main();

def main():
    message = "奥特曼-打小怪兽".encode("GBK");
    print("编码后的数据类型为：{}".format(type(message)));
    # 输出为二进制数组
    print(message);
    # 进行解码
    print(message.decode("GBK"));


if __name__ == '__main__':
    main();

View the current encoding format

# 这个组件需要下载,pip install chardet
import chardet
def main():
    message = "奥特曼-打小怪兽".encode();
    print(chardet.detect(message));


if __name__ == '__main__':
    main();

Output files in the specified format

def main():
    # w代表输出 文件不存在时，自动创建，创建成功之后写入数据
    with open("E:\\test2.txt", mode="w",encoding="UTF-8") as file:
        file.write("奥特曼打小怪兽");
if __name__ == '__main__':
    main();

The screenshots and code sources in the article are free python teaching videos from csdn